Wireless charging was all the rage in smartphones a few years ago, but most device makers have backed off on the technology. Many phones simply charge super-fast via a cable now. The wireless charging fatigue is due in part to the range limitation of the technology. True wireless power is still a no-go in consumer technology, but Disney Research has developed a version that might work in the future. Its volumetric wireless power system can keep hundreds of devices powered with no wires whatsoever. The main drawback: you have to live in a metal box.

The range of current wireless charging standards is a few inches at best, which means you can only juice up a device in a limited area — you essentially have to set it down on a charging pad. Several teams have shown off ways to transmit power over a longer distance, but they’ve come with plenty of drawbacks. While Disney’s volumetric power isn’t ideal, it’s the most feasible yet.

The researchers built a full-scale room to demonstrate the technology. The walls, floor, and ceiling are all made of aluminum panels. In the middle of the room is a copper pole that allows current to loop through the room’s structure 1.3 million times per second. A series of capacitors in the central pole make sure the electric field is confined so it doesn’t interfere with anything in the room. That’s why objects and people can walk around in the volumetric power room without harm. It meets all federal safety guidelines (mostly). Outside the room is a generator and power amplifier to pipe power into the ring of capacitors. So, clearly, this would not be a quick $49 add-on purchase when you buy a new iPhone. The looping current generates a magnetic field that fills the space, running perpendicular to the pole.

Devices with special receivers can get power from this magnetic field. The prototype room was only powering 10 devices, including a phone, a fan, and an RC car. Theoretically, it can do much more. The room is capable of pushing 1.9 kilowatts of power to devices, which is enough to keep up to 320 USB devices going. It can do all of this without affecting people in the room. The efficiency is between 40 and 95% depending on position in the room, which isn’t that far off from existing wireless charging systems.

This is just a proof of concept for now. There’s no guarantee a system based on this could be built to power devices within an existing room — aluminum paneling isn’t cheap. It is also unsafe for humans to get within 46 centimeters (18 inches) of the central pole. The team notes that smaller versions like toy chests and workspaces that charge devices might be a good first step.